Conventional microporous crystalline silicoaluminophosphates such as SAPO-11 may be prepared by hydrothermal crystallization of silicoaluminophosphate gels containing a molecular structure forming template. SAPOs are members of a class known as non-zeolitic molecular sieves. SAPO molecular sieves have a framework of AlO.sub.4, SiO.sub.4 and PO.sub.4 tetrahedra linked by oxygen atoms. The negative charge in the network is balanced by the inclusion of exchangeable protons or cations such as protonated amines or alkylamonium. The interstitial spaces of channels formed by the crystalline network enables SAPOs to be used as molecular sieves in a manner similar to zeolites, which are crystalline aluminosilicates.
More recently a new silicoaluminophosphates have been prepared that are isostructural with conventional SAPO-11, but having a dramatically higher silicon:aluminum ratio and appropriate silicon distribution. Such materials are prepared from microemulsions.
Conventional SAPOs may be used as catalysts in petroleum processing. For example, SAPO catalysts may be used in lubricating oil hydroconversion procedures, hydrocracking, dewaxing, and combinations thereof. Conventional SAPO catalysts may also be used in naphtha cracking processes for forming light olefins such as propylene.
There remains a need, though, for improved silicoaluminophosphates for use in hydrocarbon processing.